Expression of Hox genes in deuterostomes – the Hox gene cluster is duplicated in vertebrates. There are eight Hox gene clusters in teleost fishes, showing an additional duplication from the four Hox gene clusters found in the tetrapod vertebrates. (Credit: B J Swalla, Heredity) #NPG
All the cells in all animals have a complete set of genes with the instructions for building an organism. Working with mutations in fruit flies, scientists have found a group of regulatory genes called Hox genes that signal other genes in sequence to build the body of an animal. All animals except sponges have Hox genes.